Ebeneze Gee Bee R1

ebeneezer Tue May 22, 2012 12:14 pm

Hi, I am planning to build an all balsa profile, 21 inch span, freeflight Gee Bee R1. (Ebeneezer)
Will a Cox 0.49 be too powerfull?
Second question. Although a profile design I plan to a have a full cowl. Is there a some kind of extended glo clip I can use.The cowl is 4 inches in diameter.
If not, my plan is to fix the two wires to the head somehow. Then fix the other end of the two wires to a jackplug socket on the outside of the cowl. Any ideas?

Thanks.

**Cribbs74** Tue May 22, 2012 12:19 pm

With a 21 inch span a .020 would probably be a better choice. You could affix leads to the head or just snap a standard cox issue glow clip in place and run the leads as you suggested.

ebeneezer Tue May 22, 2012 12:31 pm

Thanks. The 0.49 I'm planning to use is the one out of my sons Cox PT 19 controliner circa 2000
Its one I've got and it doing nothing. I dont think its a very good one. It seems too have a lot of end float on the prop shaft. If it's run for an hour thats all it has ever run

**Cribbs74** Tue May 22, 2012 12:57 pm

ebeneezer wrote:Thanks. The 0.49 I'm planning to use is the one out of my sons Cox PT 19 controliner circa 2000
Its one I've got and it doing nothing. I dont think its a very good one. It seems too have a lot of end float on the prop shaft. If it's run for an hour thats all it has ever run

Well, it will fly it if all is balanced well. I would run it a tad rich or that FF may get away from you.

As to the float as long as the crank pin is not rubbing the backplate then it should be ok. All Cox engines have this to a varying degree. It can be corrected by adding a thrust washer behind the driveplate.

ebeneezer Tue May 22, 2012 1:07 pm

I thought about a thrust washer. Where would the best place be to get one?

**RknRusty** Tue May 22, 2012 1:07 pm

Can you put enough prop on it to blow past the 4" cowl?

**RknRusty** Tue May 22, 2012 1:09 pm

ebeneezer wrote:I thought about a thrust washer. Where would the best place be to get one?

Thrust washers can be found at http://coxengines.ca/
or
http://www.exmodelengines.com/home.php?cat=250
Bernie and Matt are both are members here.

ebeneezer Tue May 22, 2012 3:25 pm

Thanks, I'll get some

nitroairplane Tue May 22, 2012 3:32 pm

ebeneezer wrote:Hi, I am planning to build an all balsa profile, 21 inch span, freeflight Gee Bee R1. (Ebeneezer)
Will a Cox 0.49 be too powerfull?
Second question. Although a profile design I plan to a have a full cowl. Is there a some kind of extended glo clip I can use.The cowl is 4 inches in diameter.
If not, my plan is to fix the two wires to the head somehow. Then fix the other end of the two wires to a jackplug socket on the outside of the cowl. Any ideas?

Thanks.

I'd say go for it, 5x3 prop on backwards and running rich.
If it need more power flip the proper over and lean it out.
Do not over fill the tank!

Ivanhoe Tue May 22, 2012 5:51 pm

nitroairplane wrote:
ebeneezer wrote:Hi, I am planning to build an all balsa profile, 21 inch span, freeflight Gee Bee R1. (Ebeneezer)
Will a Cox 0.49 be too powerfull?
Second question. Although a profile design I plan to a have a full cowl. Is there a some kind of extended glo clip I can use.The cowl is 4 inches in diameter.
If not, my plan is to fix the two wires to the head somehow. Then fix the other end of the two wires to a jackplug socket on the outside of the cowl. Any ideas?

Thanks.
I'd say go for it, 5x3 prop on backwards and running rich.
If it need more power flip the proper over and lean it out.
Do not over fill the tank!

One problem I foresee, 5" dia prop + 4" dia cowl = 1/2" of effective prop! sorry, dat aint gonna fly, Man!

ahrma_581 Tue May 22, 2012 8:38 pm

Maybe with a 'normal' size firewall with 3 or 4 narrow struts to support the back edge of the cowl: airflow/thrust thru the inside of the cowl. Pseudo ducted fan. (patent pending.... Smile

)

Ivanhoe Wed May 23, 2012 2:57 am

ahrma_581 wrote:Maybe with a 'normal' size firewall with 3 or 4 narrow struts to support the back edge of the cowl: airflow/thrust thru the inside of the cowl. Pseudo ducted fan. (patent pending.... )

Now, THAT'S an idea!! Huh...

Kim Wed May 23, 2012 3:36 am

OR...with a nod to Indra...a Diesel conversion, turning a larger prop....

Ivanhoe Wed May 23, 2012 3:41 am

ebeneezer wrote:I thought about a thrust washer. Where would the best place be to get one?

Just a thought re- end play. Have you checked that the prop driver is properly seated on the shaft? you may be able to knock it back a little to take up some of the play

Wilf

ebeneezer Wed May 23, 2012 3:42 pm

Me again.
That front cowl/ducted fan idea sounds like an interesting idea. I 'm excited enough to want to try it.
I'll post some pics and flying report if anyone intrested. I just need to tissue cover my Slicker Mite first

nitroairplane Wed May 23, 2012 3:49 pm

Kim wrote:OR...with a nod to Indra...a Diesel conversion, turning a larger prop....

Yes but imagine a (Roughly) 7oz plane with a 21" WS and a 7x4 doing 11k, corkscrew moment lol.
Well only one way to find out for sure.....
I mean depending it all depends on the final weight doesn't it?
Wilf:

This was talked aout in another thread involving a large cowl and eventually we figured it should work, I think it was Ron's Dumas build or something.

**Cribbs74** Wed May 23, 2012 4:55 pm

nitroairplane wrote:
Kim wrote:OR...with a nod to Indra...a Diesel conversion, turning a larger prop....
Yes but imagine a (Roughly) 7oz plane with a 21" WS and a 7x4 doing 11k, corkscrew moment lol.
Well only one way to find out for sure.....
I mean depending it all depends on the final weight doesn't it?
Wilf:

This was talked aout in another thread involving a large cowl and eventually we figured it should work, I think it was Ron's Dumas build or something.

Yeah it was mine. Except the Dumas Laird has a 24" span and two wings. It's stubby but, not as stubby as a GeeBee. Plus the vertical stab is a biggun.

I was tinkering with the idea of drilling holes through the back of the nose block area as well. Glad to know others have done or considered it so it's not some crazy hair-brained idea.

Ivanhoe Wed May 23, 2012 4:58 pm

nitroairplane wrote:
Kim wrote:OR...with a nod to Indra...a Diesel conversion, turning a larger prop....
Yes but imagine a (Roughly) 7oz plane with a 21" WS and a 7x4 doing 11k, corkscrew moment lol.
Well only one way to find out for sure.....
I mean depending it all depends on the final weight doesn't it?
Wilf:

This was talked aout in another thread involving a large cowl and eventually we figured it should work, I think it was Ron's Dumas build or something.

It was my build, and it does work, but not very well! But mine wasn't as extreme as a 4" cowl and a 5" prop! that gives you 1/2" of prop outside the cowl, and the least efficient bit of the prop as well.

nitroairplane Wed May 23, 2012 5:35 pm

True but still think it would work lol I'm a stubborn one!

ebeneezer Thu May 24, 2012 8:40 am

Hi, me again. I've been routing through my Dads Cox spares, I've had his Cox engines. I've come across a diesel convertion or bits of one. What I have is a new barrel and anodised red head with a black knurled compression screw. There is also a piston down the barrel that seems very tight. Does it need some freeing oil and then, just pulling out? Do I just then just Change the head and piston on my 0.49 and run on ordinary diesel fule. Or is ther a lot more to it than that. If I can do it what size prop could I use?

GermanBeez Thu May 24, 2012 9:22 am

first of all, soak the thing in fuel for about an hour or so.
then, gently try to pull that piston out of there (without the head being screwed on, otherwise it'll pull a vacuum Wink

)
if that doesnt work, carefully heat the outside of the cylinder up with a lighter, so the gummed up stuff loosens.
if you plan on running that thing, you should get a reenforced crank shaft (check bernies diesel/killer cranks), and then you should be just fine. fuel-wise, use a mixture of ether (obtainable through starter spray), gasoline, and castor oil.
welcome to the forum, mate Wink

Beez

ebeneezer Thu May 24, 2012 11:29 am

Thanks Bees I'll do that, I've never seen or heard a Cox diesel.
What size prop can I use?
Do I need a speacial tool to seperate the conrod from the crank shaft?

John Goddard Thu May 24, 2012 11:39 am

ebeneezer wrote:Thanks Bees I'll do that, I've never seen or heard a Cox diesel.
What size prop can I use?
Do I need a speacial tool to seperate the conrod from the crank shaft?

Over here Ebz you want Model Technics D1000.
Prop? ask Nitro I think he'll say 8X4
Once the head, cylinder and back plate are off the con rod just lifts away from the crank pin/big end.
If you don't have a cox wrench, get one.
If you don't pM me your addy and I'll stick one in the post.
Very Happy

nitroairplane Thu May 24, 2012 11:49 am

Pretty much any prop 6x3-8x4 just get a head and a HD crank.
Both available from Cox internationals website.
Then head to your local hobbystores and pick up some D1000 fuel.

WingingIt74 Tue Jul 03, 2012 5:00 pm

ebeneezer wrote:Hi, I am planning to build an all balsa profile, 21 inch span, freeflight Gee Bee R1. (Ebeneezer)
Will a Cox 0.49 be too powerfull?

It's a Gee Bee isn't it? Smile

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